铝合金厚板静止轴肩搅拌摩擦焊接头组织及性能

doi:10.11868/j.issn.1001-4381.2020.001122

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Abstract

The stationary shoulder friction stir welding (SSFSW) processes for 2A14-T4 aluminum alloy with the thickness of 8.5 mm were performed by using the self-developed tools, and the influences of welding process parameters on the microstructure and mechanical properties of SSFSW welded joints were investigated. The results show that the SSFSW joints with smooth weld surface and defect-free for aluminum alloy thick-plate can only be obtained under the process parameter condition of lower rotational speed (rotational speed ω=400-600 r/min and welding speed v=60-120 mm/min).The weld zone of SSFSW joints mainly consists of nugget zone (NZ), and the widths of thermo-mechanically affected zone (TMAZ) and the heat affected zone (HAZ) around the NZ are obviously reduced; the NZ is similar with the shape of tool pin and it is composed of two kinds of fine equiaxed grains with different sizes, the grains on the advancing side are more finer than that of retreating side. The profiles of microhardness across the weld section present the "W" shape, the hardness values of NZ reach the 80%-90% of the base metal of hardness value, the softened region is produced between interfaces of TMAZ and HAZ, and its hardness is the lowest with the 72% of the base metal of hardness value. The tensile strengths of SSFSW joints reach the 88% of base metal under the welding parameters of ω=500 r/min, v=140 mm/min, and the fractured sites are always located at the softened zones between TMAZ and HAZ on the retreating side, exhibiting the toughness fracture features.

Key words： 2A14-T4 aluminum alloy thick-plate SSFSW microstructure characteristic mechanical property

Received: 08 December 2020 Published: 18 July 2022

ZTFLH:

TG453⁺.9

Corresponding Authors: Xinqi YANG E-mail: xqyang@tju.edu.cn

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	Articles by authors
	Xinqi YANG
	Huixin YUAN
	Zhuanping SUN
	Xinzhong YAN
	Huihui ZHAO

Cite this article:

Xinqi YANG,Huixin YUAN,Zhuanping SUN, et al. Microstructure and properties of stationary shoulder friction stir welded joints for aluminum alloy thick-plate[J]. Journal of Materials Engineering, 2022, 50(7): 128-138.

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http://jme.biam.ac.cn/EN/10.11868/j.issn.1001-4381.2020.001122 OR http://jme.biam.ac.cn/EN/Y2022/V50/I7/128

Chemical compositions of 2A14-T4 Al alloy (mass fraction/%)

SSFSW welding process parameters

Tensile specimen dimensions

Surface appearance of SSFSW butt weld

Macroscopic morphologies of SSFSW weld section under different welding parameters
(a)v=60 mm/min; (b)v=80 mm/min; (c)v=100 mm/min; (d)v=120 mm/min; (1)ω=500 r/min; (2)ω=600 r/min

Macroscopic morphology of SSFSW weld section
(ω=500 r/min, v=140 mm/min)

Grain microstructure of each zone of weld
(a)NZ; (b)AS-TMAZ; (c)RS-TMAZ-1;(d)RS-TMAZ-2;(e)AS-HAZ; (f)RS-HAZ

Grain microstructure of NZ
(a)NZ; (b)magnified morphology of region B; (c)magnified morphology of region C; (d)magnified morphology of region D

Micro-morphologies of SSFSW weld section under different welding parameters
(a)ω=500 r/min, v=60 mm/min; (b)ω=500 r/min, v=120 mm/min; (c)ω=600 r/min, v=60 mm/min; (d)ω=600 r/min, v=120 mm/min; (1)microstructure on AS of weld; (2)microstructure on RS of weld; (3)microstructure in center area of weld

Distribution of second phase in different zones of SSFW weld
(a)NZ; (b)TMAZ, HAZ; (c)base metal

Hardness distribution curves of the SSFSW joint

Distributions of second phase in NZ
(a)top; (b)medium; (c)bottom

Hardness distributions of weld at ω=500 r/min, v=60-140 mm/min
(a)top; (b)medium; (c)bottom

Tensile test results of welded joint
(a)ω=500 r/min; (b)ω=600 r/min

Macroscopic morphologies of typical fracture specimens
(a)ω=500 r/min, v=60 mm/min; (b)ω=600 r/min, v=60 mm/min; (c)ω=500 r/min, v=120 mm/min; (d)ω=600 r/min, v=120 mm/min

Fracture SEM images of tensile specimens
(a)ω=500 r/min, v=60 mm/min; (b)ω=600 r/min, v=60 mm/min; (c)ω=500 r/min, v=120 mm/min; (d)ω=600 r/min, v=120 mm/min

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